It is well-known that scouring waste liquid obtained from an organic solvent scouring process of a raw animal hair material contains animal hair grease which is useful in the field of medicine and cosmetics. Accordingly it is very important for the animal hair industry, including the wool industry, to recover the animal hair grease at an excellent quality and high efficiency.
Japanese Examined Patent Publication No. 35-10238 (U.S. Pat. No. 2,655,428) discloses a process for recovering wool grease from a scouring waste liquid obtained from an organic solvent scouring process of raw wool. In this process, the scouring waste liquid is mixed with water and a water-soluble alcohol so as to form flocks containing water-soluble substances and solid impurities such as sand, soil, and mud, derived from the raw wool material, in the mixture. The flocks are removed from the scouring waste liquid by means of a centrifuge. The resultant residual liquid is subjected to a process to evaporate the organic liquid and recover the wool grease.
Japanese Unexamined Patent Publication No. 56-57896 (U.S. Pat. No. 4,207,244) discloses another process for recovering wool grease. In this process, the flocks are formed in the scouring waste liquid containing the scouring extract and the organic solvent by using a water-soluble alcohol alone as the flock-forming agent.
As seen from the above-mentioned prior arts, the animal hair grease industry has believed that the procedure for removing water-soluble substance and solid impurities such as sand, soil, and mud from the scouring waste liquid containing the scouring extract and the organic solvent must include the use of water-soluble alcohol as a flock-forming agent.
However, the use of water-soluble alcohol as the flock-forming agent results in several disadvantages. That is, when the water-soluble alcohol is added to the scouring waste liquid, a portion of the water-soluble substances in the scouring extract is dissolved in the water-soluble alcohol and, therefore, is not contained in the resultant flocks. Even after the flocks are removed, the portion of the water-soluble substances are retained in the residual solution. When the wool grease is recovered from the residual solution by evaporating the organic solvent, the resultant wool grease contains the water-soluble substance. This causes unsatisfactory quality of the resultant wool grease.
Due to the above, the animal hair grease industry has sought a new process for high quality recovery of animal hair grease, for example, wool grease, from a scouring waste liquid obtained from a scouring process of a raw animal hair material with a hydrophobic organic solvent.